When a polymerizable liquid-crystal compound aligned in a nematic state is polymerized, then its aligned state is fixed and an optically-anisotropic shaped article is obtained. The optically-anisotropic shaped article is usable as an optically-compensatory film for liquid-crystal display devices. As the polymerizable liquid-crystal compound, used is a compound having an acrylic group that serves as a polymerizable reactive group.
For producing an optically-compensatory film, a polymerizable liquid-crystal composition containing a suitable photopolymerization initiator added thereto is first applied onto a substrate such as aligned triacetyl cellulose (hereinafter abbreviated to as TAC). Next, the polymerizable liquid-crystal composition is polymerized through irradiation electron rays such as UV rays to obtain an optically-anisotropic film in which the liquid crystal alignment is fixed (e.g., Patent Reference 1 and Patent Reference 2).
Patent Reference 1: JP-A 2001-55573
Patent Reference 2: JP-A 2001-154019
The step of irradiation with UV rays is desired to satisfy the following three conditions.
1) Room-temperature polymerization not requiring any specific heating device.
2) Open-air polymerization not requiring purging with inert gas such as nitrogen.
3) Polymerization through irradiation with UV rays for a few seconds.
When a conventional acrylic polymerizable liquid-crystal material is formed into an optically-anisotropic film according to the above-mentioned production process, then it brings about the following two problems.
1) In the mode of open-air UV curing, oxygen in air retards the curing, and a cured film could not be obtained.
2) Since its adhesiveness to the film substrate, TAC is poor, the cured optically-anisotropic film peels from TAC.
Accordingly, a polymerizable liquid-crystal compound and its composition capable of solving these problems are desired.